PYTHON-2255 Reduce default keepalive time to 120 seconds to align with Azure defaults

Author: ShaneHarvey

pymongo/pool.py

@@ -122,7 +122,7 @@ def _set_non_inheritable_non_atomic(dummy):
         """Dummy function for platforms that don't provide fcntl."""
         pass
 
-_MAX_TCP_KEEPIDLE = 300
+_MAX_TCP_KEEPIDLE = 120
 _MAX_TCP_KEEPINTVL = 10
 _MAX_TCP_KEEPCNT = 9